A MODELLED AND MEASURED 30-YEAR DUST EMISSION CLIMATOLOGY OF A PRO-GLACIAL VALLEY: WEIGHING THE IMPORTANCE OF ERODIBILITY AND EROSIVITY FACTORS

Dust emissions from pro-glacial surfaces has been shown to produce some of the largest dust fluxes ever recorded as several tens of meters thick deposits (loess). In the present climate, pro-glacial processes are globally reduced compared to the last glacial maximum counterparts, limited to higher latitudes, and yet estimated to contribute 3 – 5 percent of the global dust budget. The dust emission process is driven by high winds that are generated by temperature gradients daily or annually but are also a function of surface processes that can limit the availability of sediment. The river valleys containing the fine glacier-derived sediment are maximized when the ground is not frozen, and the valley contains little to no meltwater. The combination of the driving and limiting factors results in a relatively short window of transport of dust emissions in northern North America. However, dust emissions also rely on the timing and magnitude of winds in the region driven by local and synoptic pressure gradients, which vary seasonally and greatly limit the dust produced from these valleys even when they are unfrozen and dry. Using historical meteorological data as well as local weather stations, satellite imagery to measure changes in snow cover and river extent, a simple time-lapse camera network to observe dust emission frequency, and a 1-D dust emission model, this research demonstrates that the wind regime, is the major controlling variable for dust emissions of a pro-glacial valley in southwestern Yukon.

The approach taken for this study demonstrates the complex nature and connectivity of processes within high latitudes that can contribute to producing dust emission sources. However, with local adaption of surface wind speed from weather station data and surface observations to determine dust emission thresholds and strategic remote sensing analyses, a synopsis of historical rates of dust flux can be estimated. With these approach, comparisons can be made with future climate change scenarios that will see changes in the type, quantity, and timing of precipitation, the rate of change in temperature and in particular winter temperature, and any changes in wind speed dynamics created by glacier mass losses.